The Office of Regulatory Staff, upon order of the commission, may issue a certificate C to any applicant who does not propose in any way to solicit the transportation of persons over improved public highways outside of the corporate limits of any city or town or to operate upon a regular schedule, but who is privately employed for a specific trip and who will not solicit or receive patronage along the route. But those operators may solicit passengers (a) for destination within the corporate limits of any city or town wherein such passengers are solicited, (b) within a radius of two miles of the corporate limits of the city or town in which they are licensed to do business, and (c) upon such highways as are not served by a holder of an A or B certificate.